Vacuum coating apparatus



July 3o, 1968 c. A. BENTLEY, JR 3,394,679`

VACUUM COATING APPARATUS July 30, 1968 c. A. BENTLEY, .1R v 3,394,679

` VACUUM CQATNGA APPARATUS Filed Dec. 5, 1966 2 Sheets-Sheet 2 K Y] I United States Patent O 3,394,679 VACUUM CGATING APPARATUS Chester A. Bentley, Jr., Cohasset, Mass., assignor to Dresser Industries, Inc., Dallas, TeX., a corporation of Delaware Filed Dec. 5, 1966, Ser. No. 599,300 12 Claims. (Cl. 118-49) ABSTRACT 0F THE DISCLOSURE A vacuum coating installation including a vacuum chamber with inlet and outlet openings which snugly accommodate and maintain a vacuum seal with a moving conveyor belt possessing substrate retaining cavities.

This invention relates generally to vacuum coating apparatus and, more particularly, to apparatus of this type l for use in vacuum deposition of thin films onto insulated substrates.

There is a large and growing market for electronic components of reduced size and weight. One popular method of producing these microelectronic components entails the coating of integrated circuitry onto insulator substrates by thin film deposition techniques. Although the components produced by this process are excellent functionally, the process costs have been high primarily `'because of the requirement that the thin film deposition be accomplished under vacuum. Not only is the vacuum equipment itself relatively expensive, but the attainable quantity of product output relative to the capital equipment costs has been low because the vacuum system m-ust be cycled between atmospheric and vacuum pressures for each batch of output product.

Attempts to alleviate these problems have resulted in various types of continuous or semi-continuous vacuum coating systems wherein substrate elements are fed into a vacuum chamber for application of a desired coating and then discharged therefrom while a suitable vacuum pressure is continuously maintained. Typically, such continuous systems involve the use of inlet and outlet lock chambers through which the substrate elements p-ass during entrance into and exit from the vacuum chamber in which the coating process occurs. However, the difficulties in providing economical and efficient continuous vacuum systems for this application are sizable and the hereto-fore known systems have been less than satisfactory.

The object of this invention, t'herefore, is to provide a f Continuously operable vacuum apparatus capable of producing coated electronic components at a reduced unit cost.

One feature of this invention is the provision of a vacuum coating apparatus including a conveyor belt adapted to move into and out of an eVacua-ble chamber through openings having cross-sections, in planes perpendicular to the direction of belt movement, substantially the same as the transverse cross-section of the belt, and which retains within internal cavities the substrate elements to be coated. In this apparatus, an unbroken vacuum seal is continuously maintained between the inner surfaces of the vacuum chambers inlet and outlet openings and the outer surfaces of the conveyor belt. Thus, continuous coating is possible without periodic cycling of t'he vacuum chamber lbetween atmospheric pressure and the reduced press-ure required for the coating process.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured type wherein the vacuum chamber inlet and outlet openings have lengths greater than those of the belt cavities thereby insuring that a continuous vacuum seal will be maintained between the inner surfaces of the vacuum chamber openings and the outer surfaces of the conveyor belt.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured type wherein the cavities are formed Iby apertures extending through the conveyor belt which includes reentrant surface portions projecting into the apertures and adapted to provide coating masks by partially covering substrate elements positioned in the cavities.

Another feature of this invention is the provision of a Vacuum coating apparatus of the above featured types wherein the reentrant belt portions have oppositely facing fiat and beveled surfaces, both recessed from the top and bottom surfaces of the conveyor belt so as to form adjoining substrate and coating cavities. In this arrangement, the flat reentrant surface engages the substrate element deposited in the substrate cavity and the beveled surface functions as a coating mask which prevents a shadow effect and provides a recessed surface for accommodating coating material accumulation in the coating cavity.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured types including a substrate element feeder positioned outside the vacuum chamber and adapted to deposit substrate elements into the substrate cavities and a coating substance supplier positioned within the vacuum chamber 0n the opposite side of the belt conveyor and adapted to direct the coating substance through the coating cavity and onto that surface of the substrate element which is not masked by the reentrant belt portion.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured types wherein the substrate elements are deposited in substrate cavities lformed in the bottom surface of the belt conveyor as it enters the evacuable chamber and including conveyor belt guides having surfaces which contact the bottom surface of the conveyor belt so as to prevent dislodgment of the retained substrate elements.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured types including at least one inlet and one outlet lock chamber which Communicate with the evacuable chamber through the inlet and 'outlet openings thereof and wherein the lock chambers also include inlet and outlet openings adapted to receive and having the same cross-section as the conveyor belt.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured type including vacuum pumping means connected to each of the lock chambers and to the evacuable chamber so as to permit independent evacuation thereof.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured types wherein the belt conveyor is a continuous belt and including drive means for producing movement of the belt through the evacuable chamber.

Another feature of this invention is the provision of a vacuum coating apparatus of the above featured type wherein the conveyor :belt comprises disconnectable, interlocking belt length portions which possess cavities of different shape so as to accommodate dissimilar subst-rate elements and permit deposition thereon of various coating configurations.

These and other features and objects of the invention will 'become apparent upon a perusal of the following specification taken in conjunction with the accompanying drawings wherein:

FIG. l shows a partial schematic plan view of a preferred coating apparatus embodiment;

FIG. 2 is a partial schematic side view of the embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view taken along lines 3-3 of FIG. 2;

FIG. 4 is a cross-sectional View taken along lines 4-4 of FIG. 2;

FIG. 5 is an enlarged cross-sectional view taken along lines 5 5 of FIG. 2;

FIG. 6 illustrates an interlocking -section conveyor belt embodiment of the invention; and

FIG. 7 is a schematic illustration of a continuous belt embodiment of the invention.

Referring now to FIGS. 1-5, the evacuable process chamber 11 encloses the schematically illustrated vapor coating source 12 and has the flanged evacuation port 13 adapted for connection to a conventional vacuum pumping system (not shown). The inlet flange 14 and outlet flange 15 are aligned on opposite sides of the process chamber 11. Connected to the inlet flange 14 is the annular access tiange 16 enclosing the closely fitted plug 17 made of a suitable, good vacuum material such as polytetraiiuoroethylene resin. The rectangular, elongated slot 18 through the center of the plug 17 forms an inlet opening providing access into the process chamber 11.

Connected to the access flange 16 is the inlet lock assembly 20 including the inlet lock access flange 19 and the mating inlet lock chamber flange 21 which defines the inlet lock chamber 22. The inlet lock access iiange also encloses a fitted plug 23 having the centrally located, elongated slot 24 which provides access into the inlet lock chamber 22. Evacuation of the lock chamber 22 is accomplished through the lock evacuation port 25 adapted for connection with a conventional vacuum -pumping system (not shown). Vacuum tight seals between the various components are made with the O-ring gaskets 26.

The intermediate inlet lock chamber 27 is formed by the annular intermediate liange 28 having the evacuation port 29 adapted for connection to a suitable vacuum pumping system (not shown). Attached to the intermediate ange 28 is the intermediate access flange 31 having the centrally slotted plug 32. As shown, the intermediate inlet lock assembly 30 formed by the intermediate lock flange 28 and the intermediate access iiange 31 is identical to the inlet lock assembly 20. Similarly, there is connected to the intermediate access flange 31 the initial inlet lock assembly 34 which is structurally identical to the intermediate and inlet lock assemblies 20 and 30.

Joined to the outlet flange 15 is the annular exit flange 41 which is identical to the access flange 16 associated with the inlet flange 14. The outlet lock assembly 42 is coupled between the exit flange 41 and the intermediate outlet lock assembly 43 which is in turn connected to the linal outlet lock assembly 44. The outlet lock assemblies 42, 43 and 44 are identical to the inlet lock assemblies 20, 30` and 34 and are similarly adapted for connection to suitable pumping systems (not shown).

The conveyor belt 46 is adapted for movement into the process chamber 11 through the inlet lock assemblies 20, 30 and 34 and for exit therefrom to the outlet lock assemblies 42, 43 and 44. Support for the conveyor belt 46 is provided by the discontinuous guide track 47 which includes segments adjacent the initial inlet lock assembly 34 and final outlet lock assembly 44 as well as within each of the inlet and outlet lock chambers and the process chamber 11. Forming each of the guide track segments 47 i-s a flat base 48 which supports the bottom surface of the conveyor belt 46, side portions 49 which Contact the edges of the conveyor belt 46 and top portions 51 which overlap the outside marginal regions of the conveyor belt top surface. As shown in FIG. 3, the transverse cross-section of the uniform conveyor belt 46 is substantially identical to those through the slots in each of the closure plugs 17, 23, 32 etc., taken in a direction perpendicular to the movement of the conveyor belt 46. Thus, there is provided between the outer surfaces of the conveyor belt 46 and the inner surfaces of the individual plug slots a slight interference lit which permits relative movement between the conveyor belt and the plugs while also providing a vacuum seal therebetween. The various system flanges and the conveyor belt 46 are preferably made of a good vacuum :material such as stainless steel.

As shown most clearly in FIG. 5, the conveyor belt 46 possesses a plurality of spaced apart apertures 53. Each aperture 53 forms in the bottom surf-ace of the conveyor belt 46 a -substrate cavity 54 adjoining a coating cavity formed in the upper surface thereof. Partially separating the substrate cavities 54 and coating cavities 55 are the reentrant belt portions 56 which project into the apertures 53, as shown. The reentrant belt portions 56 have flat bottom surfaces 57 adapted to accommodate the llat surface of a substrate element and beveled upper surfaces 58 which are inwardly tapered to prevent formation of a shadow effect during coating of a retained substrate element. The recessed beveled surfaces 58 also are capable of supporting a limited accumulation of coating material without changing the clearance between the plug slots and the upper surface of the conveyor belt.

To operate the invention, one either constructs or selects a suitable conveyor belt 46 having substrate cavities 54 with shapes which closely conform to those of substrate element discs which are to coated and with reentrant portions 56 whose edges form the shape of the desired coating. The cavities and reentrant mask portions formed in the conveyor belt 46 may be of uniform shape or may be, as shown in FIG. 6, of varying form depending upon the final coated product requirements of a particular application. Also, as shown in FIG. 6, a desirable flexibility of output may be attained by utilizing a conveyor belt formed by individual belt segments 62 having various cavity forms 61 and interlocked by, for example, male-female socket connections 63.

After selecting an appropriate conveyor belt, substrate elements are positioned either manually or by suitable mechanical :means into the accommodating substrate cavities 54 and the conveyor belt 46 pulled ywith suitable drive means through the process chamber 11. Depending upon application, the conveyor belt 46 may be either non-continuous or continuous. `In the latter case, the schematic arrangement illustrated in FIG. 7 is desirable. As shown, the conveyor belt 46 is driven by the rotary driver 65 around the rotary guide wheel 66, and through the inlet locks 67, the .processing chamber 68 and the outlet locks 69. Positioned at the entrance to the inlet locks 67 and below the entering conveyor belt 46 is a substrate feed device 71 which automatically positions individual substrate elements into the substrate cavities 54. The schematically illustrated discharge device 72 is adapted to remove the coated substrate elements from the substrate cavities 54 after discharge from the outlet locks 69.

As the conveyor belt 46 moves through the coating apparatus, the individual substrate elements will pass through decreasing pressure zones within the inlet lock chambers, into the process chamber 11 maintained at a desired processing pressure, and through increasing pressure zones within the outlet lock chambers nally exiting into the atmosphere. For example, the belt retained substrate elements may pass through inlet lock chambers maintained, respectively, at 10 torr, .1 torr and 10-6 torr before entry into the process chamber also maintained at 10-6 torr. Similarly, after discharge from the chamber 11, the substrate elements may pass through outlet chamber lock chambers maintained at, respectively, 10-6 torr, .1 torr and l0 torr. It will be appreciated that the use of plural inlet and outlet lock chambers to reduce pressure differentials between adjacent volumes is desirable since the vacuum seal provided between the relatively movable surfaces of the conveyor belt 46 and the closure plug elements cannot be made absolute according to known practical sealing methods. In this regard, it is `highly preferred that the slotted plugs 17, 23, 32, etc., have a :length greater than the maximum dimension of the cavities 54 and 55 in the direction of conveyor belt movement. This prevents formation by the cavities 54 and 55 of relatively high conductance leak paths between adjacent chambers.

Obviously, many modications and variations of the present invention are possible in light of the above teachings. For example only, the device may be used for coating substrate elements having shapes other than those illustrated or the position of the conveyor belt 46 may be reversed with the substrate cavities 54 positioned in the top portion thereof and the coating device 12 positioned below the belt. Similarly, a conveyor belt may be provided which does not function as a substrate mask but merely serves to retain and transport the individual substrate elements through the processing chamber. In this case, suitable coating masks (not shown) may be rigidly supported within the processing chamber between the coating source and the movable conveyor belt. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A vacuum coating apparatus comprising an evacuable chamber having an inlet and an outlet opening, coating means positioned within said evacuable chamber, belt conveyor means adapted for movement into and lout of said evacuable chamber through said inlet and outlet openings, said belt conveyor means having a transverse cross section of uniform size substantially the same as the cross sections of said inlet and outlet openings in planes perpendicular to the direction of movement of said belt conveyor means, said belt conveyor means having a plurality of apertures extending therethrough and including reentrant portions extending into said apertures, each aperture and associated reentrant portions dening a substrate cavity opening to one surface of said belt conveyor means adapted to receive a substrate element to be coated and a coating mask adjacent to the opposite surface of said belt conveyor means partially covering the substrate element positioned in said cavity, guide means adapted to guide movement of said belt conveyor means through said evacuable chamber and adjacent said coating means so as to allow coating thereby of substrate elements positioned in said cavities, and said guide means comprising support surface means which engage said one surface of said belt conveyor means to prevent dislodgement of substrate elements from said cavities.

2. A Vacuum coating apparatus according to claim 1 wherein said reentrant portions are recessed from both top and bottom surfaces of said belt conveyor means.

3. A vacuum coating apparatus according to claim 2 wherein each of said apertures comprises a substrate cavity located on one side of said reentrant portion and adapted to receive a substrate element, and a coating cavity located on the opposite side of said reentrant surface portion.

4. A vacuum coating apparatus according to claim 1 wherein said inlet and outlet openings are of a length greater than the greatest dimension of said apertures in the direction of movement of said belt conveyor means.

5. A vacuum coating apparatus according to claim 1 including a substrate element supply means positioned outside said evacuable chamber on one side of said belt conveyor means and adapted to deposit substrate elements into said substrate cavities and wherein said coating means is positioned on the opposite side of said belt conveyor means.

6. A vacuum coating apparatus according to claim 1 wherein said belt conveyor means is a continuous belt and including drive means for producing movement of said continuous belt through said evacuable chamber.

7. A vacuum coating apparatus according to claim 1 wherein said belt conveyor means comprises disconnectable interlocking belt length segments.

8. A vacuum coating apparatus according to claim 1 including at least one inlet lock chamber communicating with said evacuable chamber through said inlet opening and having an inlet lock 4opening adapted to receive said belt conveyor means, and at least one outlet lock chamber communicating with said evacuable chamber through said outlet opening and having an outlet lock opening adapted to discharge said belt conveyor means and wherein said inlet lock and said outlet lock openings have cross sections in planes perpendicular to the direction of movement of said belt conveyor means substantially equal to said belt conveyor means transverse cross section.

9. A vacuum coating apparatus according to claim 8 including vacuum pumping means connected to each of said evacuable chamber, said inlet lock Chamber and said outlet lock chamber.

10. A vacuum coating apparatus according to claim 8 wherein said inlet and -outlet openings are of a length greater than the greatest dimension of said apertures in the direction of movement of said belt conveyor means.

11. A vacuum coating apparatus according to claim 8 including a substrate element supply means positioned outside said evacuable chamber on one side of said belt conveyor means and adapted to deposit substrate elements into said substrate cavities and wherein said coating means is positioned on the opposite side of said belt conveyor means.

12. A vacuum coating apparatus according to claim 11 wherein said inlet and outlet openings and said inlet lock openings and said outlet lock openings are of a length greater than the greatest dimension of said apertures in the direction of movement of said belt conveyor means.

References Cited UNITED STATES PATENTS 1,771,627 7/1930 Hart lOl-122 1,839,731 1/1932 Baum.

2,286,819 6/1942 Lee 118-49 2,657,457 11/1953 Toulmin 118-48 X 3,048,146 8/1962 Coppola 118-301 3,183,563 5/1965 Smith 11S-49.1 X 3,231,065 1/1966 Kaminski et al 198-131 3,302,609 2/1967 Walker et al. 118-49 MORRIS KAPLAN, Primary Examiner. 

